Detailed Answer to Initial Practice: Determining Whether the Slope of a
Line is Positive, Negative, Infinite or Zero


  1. In the figure below, which line(s) (R, S, or T) has a positive slope? Which one(s) has a negative slope?
    In the figure, line T is sloping upward. This means the slope is positive.
    Both of the lines R and S slope downward, therefore they both have a negative slope.

  2. In the graphs below (a through f), which contain(s) a line with a positive slope? A negative slope? Slope of zero? Infinite slope?
    In both (a) and (c), the lines are sloping downward to the right. This means that the lines in each of these has a negative slope.  
    In both (b) and (f) below, the lines are horizontal. This means that the lines in each of these has a slope of zero.  

    In (d), the line is vertical. This means that the line in this graph has an infinite slope.
    In (e), the line is sloping upward to the right. This means that the line in this graph has a positive slope.

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